[Website] Items not available in the pull-down menu

[mhannuksela]

Summary

The "Registered Types" pull-down menu lacks the option of items.

Steps to reproduce

1. Open mp4ra.org website
2. Click "Registered Types", no "Items" or "Metadata items" appears there.

[bradh]

It looks like it's bundled into Codecs (Metadata Item Type Codes Registered to ISO down in https://mp4ra.org/registered-types/codecs). I guess it could be a separate page, not sure of what would work best given the QuickTime overlap here.